'''几次常规用法'''
for i in range(1,4):#从1开始  1 2 3
    print(i)

for i in range(4): #从0开始 0 1 2 3
    print(i)

a=[1,2,3,'ll','24']
for i in a: #遍历每个列表元素
    print(i)

b={'k1':'v1','k2':'v2','k3':'v3'}
for i in b.keys(): #遍历字典键
    print(i)

for i in b.values(): #遍历字典值
    print(i)

for k,v in b.items(): #键值对一起遍历
    print(k,v)